This is a chart of my daily mood average since May 15, so roughly 5 months. I track my mood with an iPhone app called MoodKit. I recommend it if, like me and many with ADD/ADHD, you find yourself struggling to control your moods.
This app has other tools as well to help manage how you feel. But the one thing it doesn't have is a way to track multiple moods per day. It could allow for that and still show a daily average. As you can see, I averaged an upbeat day this last month.
But that doesn't tell the story. My problem is that I have quick mood shifts lasting usually no more than a few hours. So, the first half of my day might be 9/10, while the second might drop to 5/10. But the average is 7, as if I had a fairly good day, which clearly isn't true.
Anyway, given the apparent prevalence of the problem, it makes sense that anyone with ADD/ADHD should track moods and I've found this an easy way to do it. If you don't have an iPhone, there are other options, like websites, forums, and, if you don't care about trees, pen and paper, that might serve you just as well.